Muscle Spindles removed at muscle biopsy from normal volunteers will be studied with the electron microscope and compared with spindles from volunteer patients with amyotrophic lateral sclerosis, Charcot-Marie-Tooth disease, and polymyositis. At biopsy, portions of muscle known to contain muscle spindles are removed and placed in glutaraldehyde fixative. Under a dissecting microscope muscle spindles are located and isolated from all extrafusal muscle. After post fixation in osmium tetroxide portions of the spindle selected for special study are cut out of the whole mount for further preparation and study with the electron microscope. Because of their physiological importance the primary sensory endings, motor endings, intrafusal muscle fibers and the pole of the capsule will receive special attention. The description of normal human spindle structure will provide a base line for correlation with similar anatomical research on other species and provide the anatomical basis for future physiological work. The study of pathological material will aid in our understanding of the alterations in voluntary and reflex motion exhibited by these patients.